2016 Volume 41 Issue 4 Pages 171-174
Twenty arylsulfonamide derivatives containing 2-arylamino-4(3H)-quinazolinone were synthesized and evaluated for their bioactivities. 4-Fluoro-N-(2-(4-oxo-2-(4-(trifluoromethoxy)phenyl)amino)quinazolin-3(4H)-yl)ethyl benzenesulfonamide, showed excellent activity both against Ralstonia solanacearum and Gibberella zeae with the inhibition rates of 100% (200 mg/L) and 95% (100 mg/L), and 69% (50 mg/L), respectively, exceeding that of the assigned commercial bactericide (thiodiazole-copper) and fungicide (hymexazol). The preliminary structure activity relationships (SAR) showed that both benzene rings of arylamino and arylsulfonamido moieties containing electron-withdrawing substitutes may be preferable for improving the bioactivity of target compounds.
Plant disease is one natural disaster that causes serious damage to agricultural production worldwide. Chemical control has been developed along with the occurrence of plant disease as one disaster reduction measure. To date, a series of high-efficiency, low-toxicity, low-residue and eco-friendly fungicides have been discovered and used widely in the prevention and control of plant diseases that have played an important role in agricultural production. Among them, sulfa fungicides—such as flusulfamide,1) tolylfluanid,2) cyazofamid,3) and amisulbrom4)—are outstanding representatives. However, plant pathogens resistant to some of the sulfa fungicides have developed rapidly in recent years. It is no longer an insignificant topic regarding integrated plant disease management.
Hence, discovering a novel sulfa fungicide is significant. In recent years, most of the effort has been focused on the investigation of sulfonamides. Li et al.5) have explored a series of cycloalkyl sulfonamides that exhibited excellent activities against Botrytis cinerea, both in vitro and in vivo. Syamaiah et al.6) have designed and synthesized novel pyrrolyl sulfonamides, and the bioassay indicated that the chloro-substituted pyrrolyl sulfonamides were potent antimicrobial agents particularly against Pseudomonas aeruginosa and Penicillium chrysogenum. Zheng et al.7) have reported a series of novel acylsulfamoylbenzamide analogues, and some of the compounds showed excellent activity against Physolospora piricola.
Those works are excellent, however, the introduction of 2-arylamino-3-aminoethyl 4(3H)-quinazolinones to sulfonamides has rarely been reported. To our knowledge, a 4(3H)-quinazolinone moiety is a class of important functional groups. Additionally, compounds containing the moiety have broad-spectrum, high-efficiency bioactivities, such as bactericidal,8,9) antipyretic,10) analgesic,11) fungicidal,12) antitetanic,13) antihypertensive,14) anticancer15) activities and so on. Motivated by the function of the 4(3H)-quinazolinone moiety, we have first described an efficient protocol for synthesizing of 3-aminoalkyl-2-arylaminoquinazolin-4(3H)-ones via an aza-Wittig reaction.16) Song group has synthesized some novel arylimine derivatives containing the 4(3H)-quinazolinone moiety.17,18) The bioassay indicated that some of the compounds also had strong antibacterial activities against pathogens of rice bacterial blight as well as tobacco and tomato bacterial wilts. Recently, we have published a series of novel 4(3H)-quinazolinone Schiff base derivatives, and some of the analogues showed good to excellent activities against Phomopsis mangiferae and Corynespora cassiicola.19)
Therefore, according to the drug design principle of bioactive substructure combination, the bioactivities of sulfonamides would be enhanced, while the functional groups, 4(3H)-quinazolinones, were introduced. Based on this hypothesis, we herein aimed to synthesize of a series of arylsulfonamide derivatives containing 2-arylamino-4-(3H)-quinazolinone by assembling aminoethyl quinazolinone and arylsulfonyl chloride. We also studied their biological activities.
All chemical reagents were commercially available and treated with standard methods before use. Solvents were dried in a routine way and redistilled before use.
1.1. Preparation of 3-(2-aminoethyl)-2-(arylamino)-4(3H)-quinazolinones 1a–1dThe key intermediates, 3-(2-aminoethyl)-2-(arylamino)-4(3H)-quinazolinone (1a–1d), were prepared from the starting material o-aminobenzoic acid. The overall yield was 35%–91%. The details can be found in our previous publication.16)
1.2. Preparation of target compounds 3a–3t3-(2-Aminoethyl)-2-(arylamino)-4(3H)-quinazolinone 1 (1.0 mmol) and dichloromethane (DCM, 10 mL) were added into a dry flask. After substrate 1 was dissolved completely, triethylamine (2 mL) was added. Then, fresh arylsulfonyl chloride 2 (1.2 mmol) was dropped slowly into the mixture by strong stirring on an ice-salt bath. Next, the reaction mixture was stirred at 40°C for about 7 hr according to TLC analysis. The final mixture was purified by chromatography on silica using petroleum ether/ethyl acetate (1 : 1) as the eluent to give the title compounds 3a–3t (data shown in supplement).
2. Biological evaluation2.1. In vitro antifungal bioassayThe fungicidal activity of the title compounds against Gibberella zeae, Fusarium oxysporum and Cytospora mandshurica was evaluated by using the mycelial growth rate method at a concentration of 50 mg/L.20,21) The fungi were provided by Kaili University, Guizhou, P. R. China. All the final compounds were dissolved in 1 mL of dimethylsulfoxide (DMSO). Mycelia dishes of approximately 4 mm in diameter were cut from the culture medium. All the strains were cultivated in potato dextrose agar (PDA) medium at 27±1°C for 4 days. The commercial fungicide hymexazol was chosen as a positive control against the above fungi under the same conditions. Meanwhile, DMSO in sterile DDW (double-distilled water) was served as a blank control. Three replicates were performed. The radial growth of the fungal colonies was measured, and the data were statistically analyzed. The relative inhibition rate of the test compounds was calculated as follows: I (%)=[(d0−d1)/(d0−4)]×100, where I stands for the inhibition rate (%), d0 (in mm) represents the diameter of fungal growth on untreated PDA, and d1 (in mm) is the diameter of mycelia in the presence of treated PDA.
2.2. In vitro antibacterial bioassayThe bactericidal activity of the title compounds against Ralstonia solanacearum and Xanthomonas oryzae was evaluated by the turbidimeter test at concentrations of 200 and 100 mg/L.18,22) R. solanacearum and X. oryzae, the causal agents of tobacco bacterial wilt and rice bacterial blight, were provided by Kaili University, Guizhou, P. R. China. They were cultivated in a nontoxic nutrient broth (NB) and M210 liquid medium, respectively. All the tested compounds were dissolved in 150 µL of DMSO and diluted with DDW containing Tween-80 (0.1%) to obtain the final concentrations as mentioned. Thiodiazole-copper served as a positive control, while DMSO in DDW served as a negative control. The inoculated pathogens of tobacco bacterial wilt and rice bacterial blight were incubated at 30±1°C with continuous shaking at 180 rpm for 48 hr and 36 hr, respectively. Culture growth was monitored with a spectrophotometer by measuring the optical density at 600 nm (OD600) given by corrected turbidity values. The relative inhibition rate (I %) was calculated via the following formula: I (%)=[(C−T)/C]×100, in which C is the corrected OD value of bacterial growth of the blank control, and T is the corrected OD value of bacterial growth of the treated ones.
A series of arylsulfonamide derivatives containing 2-arylamino-4-(3H)-quinazolinone were obtained based on their synthetic feasibility and synthesized with moderate to good yields by the following reactions outlined in Scheme 1 and Scheme 2, respectively. Initially, the synthesis of the key intermediates, 3-(2-aminoethyl)-2-(arylamino)-4(3H)-quinazolinones (1a–1d), was carried out via an aza-Wittig reaction by employing commercially available 2-amino-4-chlorobenzoic acid as the starting material (Scheme 1). Further treatment of these domino reactions was implemented according to our previous publication.16) The subsequent sulfonylation of 3-(2-aminoethyl)-2-(arylamino)-4(3H)-quinazolinones with the substituted arylsulfonyl chlorides in DCM under basic conditions afforded the corresponding title 4(3H)-quinazolinone arylsulfonamide conjugates (3a–3t) as illustrated in Scheme 2. The structures of all target compounds were determined by 1H NMR, IR, MS and elemental analysis. The spectroscopic data were in accordance with their assigned structures.
a: NaNO2, HCl, 0–5°C; b: NaN3, CH3COONa·3H2O, 0–5°C; c: CH3CH2OH, SOCl2, 6 hr; d: PPh3, CH2Cl2, rt, 10 hr; e: R1NCO (R1=C6H5, 3-CH3–C6H4, 4-CH3–C6H4, 4-OCF3), 0–5°C, 10 hr; f: H2NCH2CH2NH2, CH2Cl2, rt, 10 hr. 1a: R1=H; 1b: R1=3-CH3; 1c: R1=4-CH3; 1d: R1=4-OCF3.
3a: R1=H, R2=F; 3b: R1=H, R2=Cl; 3c: R1=H, R2=Br; 3d: R1=H, R2=CH3; 3e: R1=H, R2=OCH3; 3f: R1=3-CH3, R2=F; 3g: R1=3-CH3, R2=Cl; 3h: R1=3-CH3, R2=Br; 3i: R1=3-CH3, R2=CH3; 3j: R1=3-CH3, R2=OCH3; 3k: R1=4-CH3, R2=F; 3l: R1=4-CH3, R2=Cl; 3m: R1=4-CH3, R2=Br; 3n: R1=4-CH3, R2=CH3; 3o: R1=4-CH3, R2=OCH3; 3p: R1=4-OCF3, R2=F; 3q: R1=4-OCF3, R2=Cl; 3r: R1=4-OCF3, R2=Br; 3s: R1=4-OCF3, R2=CH3; 3t: R1=4-OCF3, R2=OCH3.
The inhibitory effects of the synthesized arylsulfonamide derivatives of 2-arylamino-4-(3H)-quinazolinone on the three phytopathogenic fungi (G. zeae, F. oxysporum and C. mandshurica) were studied, and the mycelial growth rate method was selected for screening fungicidal activity. The results were shown in Table 1. At a concentration of 50 mg/L, the inhibition rates of the final products 3a–3t against G. zeae, F. oxysporum and C. mandshurica ranged from 5.81±0.66 to 68.56±0.71, from 0 to 50.76±1.32, and from 0 to 41.97±1.78, respectively. Additionally, the inhibition rates of the positive control, a broad-spectrum fungicide named hymexazol, against the corresponding fungi were 55.54±3.90, 56.12±4.10, and 49.61±7.84, respectively. Obviously, not all of the resultant compounds were sensitive to the tested fungi. However, as compared with hymexazol, compound 3p exhibited good potency against G. zeae (68.56±0.71 vs. 55.54±3.90), while the inhibitory effect of compound 3q against G. zeae was equal to the commercial fungicide hymexazol (54.91±1.36 vs. 55.54±3.90).
| Compd. | Inhibition rate±SE/% (n=3) | ||
|---|---|---|---|
| G. zeae | F. oxysporum | C. mandshurica | |
| 3a | 25.69±0.76 | 7.28±1.17 | 0 |
| 3b | 22.63±0.99 | 0 | 0 |
| 3c | 11.31±1.15 | 0 | 0 |
| 3d | 9.48±0.94 | 0 | 0 |
| 3e | 14.37±1.27 | 0 | 0 |
| 3f | 25.99±1.18 | 9.18±1.44 | 41.97±1.78 |
| 3g | 21.71±1.01 | 7.91±1.53 | 3.61±0.79 |
| 3h | 19.88±1.72 | 0 | 0 |
| 3i | 11.31±0.68 | 0 | 0 |
| 3j | 15.08±0.92 | 0 | 0 |
| 3k | 15.29±0.65 | 22.78±1.97 | 0 |
| 3l | 12.54±1.16 | 21.84±1.80 | 0 |
| 3m | 9.48±1.04 | 14.87±1.00 | 0 |
| 3n | 5.81±0.66 | 4.76±1.21 | 0 |
| 3o | 6.73±0.62 | 4.90±0.84 | 0 |
| 3p | 68.56±0.71 | 50.76±1.32 | 0 |
| 3q | 54.91±1.36 | 50.25±2.02 | 0 |
| 3r | 51.93±0.73 | 48.86±1.48 | 0 |
| 3s | 46.70±1.55 | 14.24±1.40 | 0 |
| 3t | 48.79±0.63 | 21.52±0.94 | 0 |
| Hymexazol | 55.54±3.90 | 56.12±4.10 | 49.61±7.84 |
| DMSO | 0 | 0 | 0 |
Two kinds of plant pathogens, namely, phytopathogenic bacteria (tobacco bacterial wilt and rice bacterial blight) were chosen for bioassay by the turbidimeter test. The commercial bactericide thiodiazole-copper was served as a reference. As shown in Table 2, the bacteriostatic effects of the target compounds against R. solanacearum were much better than against X. oryzae at the corresponding concentrations. Additionally, some target compounds displayed excellent activities against R. solanacearum as compared with the standard drug thiodiazole-copper at 200 mg/L. Especially, compound 3p exhibited notable activity against R. solanacearum with an inhibition rate of 100%. Meanwhile, the antibacterial activities of compounds 3q, 3r, 3s and 3t against R. solanacearum at 200 and 100 mg/L were 92 and 75%, 92 and 70%, 80 and 55%, and 84 and 60%, respectively, which were much higher than those of thiodiazole-copper (55% and 37%). Additionally, the antibacterial activities of compounds 3k and 3l against R. solanacearum at 200 mg/L were also exceeding or equal to that of the positive control thiodiazole-copper (67% vs. 55% and 56% vs. 55%, respectively).
| Compd. | Inhibition rate % (n=3) | |||
|---|---|---|---|---|
| R. solanacearum | X. oryzae | |||
| 200 mg/L | 100 mg/L | 200 mg/L | 100 mg/L | |
| 3a | 47 | 18 | 26 | 17 |
| 3b | 40 | 17 | 23 | 10 |
| 3c | 37 | 16 | 19 | 10 |
| 3d | 24 | 11 | 8 | 0 |
| 3e | 28 | 12 | 12 | 0 |
| 3f | 51 | 20 | 31 | 12 |
| 3g | 48 | 20 | 27 | 10 |
| 3h | 45 | 19 | 22 | 0 |
| 3i | 32 | 10 | 0 | 0 |
| 3j | 36 | 17 | 0 | 0 |
| 3k | 67 | 25 | 29 | 17 |
| 3l | 56 | 24 | 26 | 15 |
| 3m | 48 | 21 | 20 | 13 |
| 3n | 41 | 15 | 12 | 11 |
| 3o | 47 | 17 | 20 | 10 |
| 3p | 100 | 95 | 33 | 25 |
| 3q | 92 | 75 | 29 | 22 |
| 3r | 92 | 70 | 29 | 22 |
| 3s | 80 | 55 | 23 | 12 |
| 3t | 84 | 60 | 25 | 18 |
| Thiodiazole-copper | 55 | 37 | 40 | 35 |
| DMSO | 0 | 0 | 0 | 0 |
According to the antimicrobial values listed in Tables 1 and 2, the relationships between antimicrobial activities and different aryl groups were studied. Generally, the differences of R1 and R2 groups affected the fungicidal and bactericidal activities. In particular, the electronegativity of R1 was important for bioactivity. When R1 was OCF3, the antimicrobial bioactivity of the analogues could be dramatically improved. The R1 group of synthesized compounds substituted with OCF3 gave better activity than that substituted with H and CH3. Meanwhile, when R2 was F, Cl or Br, the compounds also displayed higher activities than that of OCH3 or CH3. Moreover, when R1 and R2 were both substituted with OCF3 and halogen (F, Cl and Br), respectively, the compounds exhibited excellent bioactivity (e.g., 3p, 3q and 3r). It may be inferred that both benzene rings of arylamine and arylsulfonamide moieties with electron-withdrawing substitutes were beneficial to enhance the bioactivity.
To sum up, twenty arylsulfonamide analogues containing a 4-(3H)-quinazolinone nucleus were synthesized. And their bioactivities including in vitro antifungal and antibacterial activities were also evaluated. The bioassay results indicated that the title compounds tended to control pathogenic bacteria well. Compound 3p showed great promise as a lead compound for further bactericidal discovery. Preliminary SAR analysis revealed that the electronic effect may be one important factor affecting the bioactivity of the title compound. Both benzene rings (arylamine and arylsulfonamide moieties) being substituted with electron-withdrawing groups were preferable for improving the bioactivity of the target compounds. The further study of 4-(3H)-quinazolinone arylsulfonamide derivatives would be beneficial.
This study was funded by the Science and Technology Program of Hubei Provincial Department of Education, China (No. B2016200), and the Joint Funds of the Natural Science Foundation of Guizhou Province, China (No. LKK[2013]03).
